５
MEASUREMENT OPERATION
5-226
TMPM5200-2
in this selection box instead of specifying the
source gain. Three gains are provided, as shown below:
•
Preamp Gain
Concerning the tunneling current signals (Current and Log current), specify the gain
for the tunneling current preamplifier
Gain
Tunneling current
1 V/nA
0 to 10 nA
0.1 V/nA
0 to 100 nA
0.01 V/nA
0 to 1
µ
A
Usually, select 1 V/nA for the ordinary STM mode, but if a tunneling current
exceeds 10 nA in the I-V measurement, or if a contact curren
A in the
contact current measurement in the AFM Contact mode, se
or 0.01
V/nA.
In the contact current measurement, if the current is too large, the cantilever tip
and the specimen could be damaged by Joule heat. Be careful not to set too
large a bias voltage.
t exceeds 10 n
lect 0.1 V/nA
